These studies will explore the role of nutritional factors -- specifically, fat consumption -- in the development and maintenance of human obesity. The studies introduce a new instrument for the assessment of dietary intake in the obese, and combine nutritional and behavioral assays to investigate metabolic, sensory, and behavioral variables that may underlie individual preferences for high-fat foods or determine the selection of high-fat diets. Examination of the links between the reported type and quantity of dietary fats, serum lipids, and age, sex, and obesity status has important clinical implications in the development of dietary treatment or prevention modalities for obesity and coronary heart disease. The studies will employ a community sample of healthy obese males and females, including adults, ages 25-44, and adolescents, ages 12-17, as well as appropriately matched lean controls. Obese mothers, ages 25-44, and their children, ages 6-11, at risk for developing obesity will be compared to a group of matched lean controls and their children. The subjects' weights will be stable or increasing: all dieters will be eliminated from the study. Obesity will be defined as weight above 85th percentiles (NHANES data). Further classification of obesities will be based on family pedigree, age of onset of obesity, weight history and the percentage and distribution of body fat. Reported intake data for calories, saturated and unsaturated fats, cholesterol, sugar and sodium will be analyzed as a function of age, sex, and obesity status. To investigate the association between reported energy intake, obesity status and serum lipids, measures of serum cholesterol, LDL, HDL-2 and HDL-3 cholesterol, triglycerides, plasma fatty acids, and apolipoproteins (Apo A-I and Apo-B) will be obtained. Plasma beta-hydroxybutryrate and HbA1c levels will be used as additional indices of energy status. Profiles of sensory perceptions and preferences for fat- and sugar-containing stimuli will be examined as a function of sex, age, and obesity status. Behavioral factors related to the development of food habits and the selection of a high-fat diet will also be examined.